Explore Dr. Retzler’s HormoneSynergy® Longevity Medicine Resource Library

Longevity Medicine, Functional Wellness & Anti-Aging Insights from HormoneSynergy®

Welcome to the HormoneSynergy® Longevity Medicine Blog, a physician-guided clinical library led by Dr. Kathryn Retzler. Our articles cover the systems that most often shape health with age: metabolic health, hormones, cardiovascular and kidney risk, body composition, bone and muscle, brain health, sleep, gut health, nutrition, supplements, and the biology of aging.

The library is organized around clinical questions rather than trends. Some articles review new research. Others explain testing, treatment, nutrition, or a condition patients commonly encounter. Across the collection, the standard is the same: evidence first, appropriate uncertainty, and enough clinical context to separate useful medicine from wellness marketing.

Start with the HormoneSynergy® Longevity Medicine Framework

New & recently updated:

Metabolic Health & Insulin Resistance

Clinical resources on insulin resistance, glucose regulation, metabolic syndrome, visceral fat, prediabetes, obesity and GLP-1-based care within a broader longevity medicine plan.

Kidney Health & Cardiovascular-Kidney-Metabolic Health

Kidney health belongs in the same clinical conversation as blood pressure, diabetes, insulin resistance, obesity and cardiovascular risk. These resources cover early detection, CKD, albuminuria, nutrition and CKM health.

Gut Health, Microbiome & Immune Signaling

Clinical education on the microbiome, intestinal barrier, fiber, inflammation, gut-brain signaling, immune biology and the growing connections between gut, metabolic and kidney health.

Food Quality, Vitamins, Supplements & Wellness Claims

Evidence-based guidance on nutrient gaps, supplement quality, interactions, food claims and longevity products, with an emphasis on where supplementation helps and where marketing outruns the evidence.

  • HOMA-IR Explained: An Early Estimate of Insulin Resistance

    HOMA-IR formula combining fasting insulin and fasting glucose to estimate early insulin resistance.

    HOMA-IR combines fasting glucose and fasting insulin to estimate insulin resistance during the fasting state. It can reveal compensatory hyperinsulinemia before glucose becomes abnormal, but there is no universal cutoff. This guide explains the formula, provides a worked example, and shows how to interpret the result without treating it as a diagnosis.

  • Fasting Insulin vs A1C: Which Detects Metabolic Disease Earlier?

    Fasting insulin vs. A1C infographic comparing what each test measures and how fasting insulin may reveal insulin resistance before A1C becomes abnormal.

    Fasting insulin and hemoglobin A1C measure different aspects of metabolic health. While A1C reflects average blood glucose over time, fasting insulin can reveal insulin resistance years before blood sugar rises. Understanding the difference helps detect metabolic dysfunction earlier within a longevity medicine framework.

  • Visceral Fat and Insulin Resistance: Why Fat Distribution Matters

    Visceral belly fat illustrating its role in insulin resistance metabolic dysfunction and increased risk of chronic disease HormoneSynergy® Longevity Medicine Portland • Lake Oswego • USA

    Visceral fat surrounds the abdominal organs and carries greater metabolic risk than fat stored beneath the skin. Learn how it affects insulin sensitivity, how it is measured, and which strategies can reduce it.

  • Metabolic Syndrome Explained: Criteria, Risks, and How to Improve It

    Medical illustration showing the five metabolic syndrome criteria and their relationship to cardiovascular and metabolic health.

    Metabolic syndrome is diagnosed when at least three of five common risk factors occur together. Learn what the criteria mean, how insulin resistance and visceral fat contribute, and what can improve long-term cardiometabolic health.

  • Continuous Glucose Monitoring Explained: A Longevity Medicine Guide

    Continuous glucose monitoring device tracking real-time blood sugar trends to evaluate metabolic health and insulin resistance HormoneSynergy® Longevity Medicine Portland • Lake Oswego • USA

    Continuous glucose monitoring (CGM) allows real-time insight into blood sugar patterns, helping detect early insulin resistance, metabolic dysfunction, and glucose variability. In longevity medicine, CGM provides personalized metabolic data that can guide nutrition, lifestyle changes, and preventive strategies to improve metabolic health and long-term healthspan.

  • Muscle Mass and Metabolic Health: Why Skeletal Muscle Matters for Longevity

    Skeletal muscle and metabolic health showing how muscle mass improves insulin sensitivity metabolism strength and longevity HormoneSynergy® Longevity Medicine Portland • Lake Oswego • USA

    Skeletal muscle plays a central role in metabolic health, insulin sensitivity, and long-term disease prevention. In longevity medicine, maintaining healthy muscle mass supports glucose regulation, metabolic flexibility, strength, and healthy aging while reducing the risk of insulin resistance, frailty, and cardiometabolic disease.

  • Metabolic Health & Insulin Resistance: What Happens Before Diabetes

    Insulin resistance and metabolic health showing glucose regulation, skeletal muscle, liver and visceral fat in longevity medicine

    Insulin resistance can develop while fasting glucose and A1C still look reassuring. Understanding fasting insulin, visceral fat, muscle mass, triglycerides, liver health, sleep, and glucose regulation can reveal a much larger metabolic picture before diabetes develops.

  • Resistance Training and Healthy Aging: Strength, Muscle, and Metabolic Health

    Resistance training and longevity showing strength training improving muscle mass metabolic health and long-term healthspan HormoneSynergy® Longevity Medicine Portland • Lake Oswego • USA

    Resistance training becomes increasingly important with age as muscle strength, power, and lean tissue begin to decline. The benefits extend beyond muscle size to glucose regulation, mobility, physical reserve, and the ability to remain independent.

  • Coronary Artery Calcium Score Explained: Early Detection of Heart Disease

    Coronary artery calcium score showing early detection of heart disease through CT imaging of coronary plaque and cardiovascular risk HormoneSynergy® Longevity Medicine Portland • Lake Oswego • USA

    A coronary artery calcium (CAC) score measures calcified plaque within the coronary arteries and can help identify early signs of atherosclerosis before symptoms appear. CAC scanning is increasingly used in preventive cardiology to better assess cardiovascular risk.

  • ApoB Explained: The Particle Count Standard Cholesterol Testing Can Miss

    Physician reviewing an ApoB blood test with a patient as a medical illustration shows atherogenic lipoprotein particles circulating in an artery.

    LDL cholesterol measures how much cholesterol is being carried. ApoB estimates how many potentially atherogenic particles are carrying it. When those measurements disagree, ApoB can reveal cardiovascular risk that a standard lipid panel may underestimate.

  • LDL vs ApoB: Which Better Predicts Cardiovascular Risk?

    LDL cholesterol vs ApoB comparison showing which lipoprotein marker better predicts cardiovascular risk and atherosclerosis HormoneSynergy® Longevity Medicine Portland • Lake Oswego • USA

    LDL-C measures how much cholesterol is being carried inside LDL particles. ApoB estimates how many atherogenic particles are circulating. Most of the time they agree. When they do not, ApoB can reveal cardiovascular risk that LDL-C alone may underestimate.

  • Lipoprotein(a): The Genetic Cholesterol Risk Marker

    Lipoprotein(a) genetic cholesterol marker associated with increased cardiovascular risk and early heart disease detection HormoneSynergy® Longevity Medicine Portland • Lake Oswego • USA

    Lipoprotein(a), often abbreviated Lp(a), is a genetically influenced lipoprotein associated with increased cardiovascular risk. Because Lp(a) levels are largely determined by genetics, measuring Lp(a) can provide important insight into inherited cardiovascular risk.